Method for producing sintered ore

Abstract

Disclosed is a method for producing sintered ore having a high yield by using iron ore powder having a high crystal water content and a carbon material having a low combustion initiation temperature. A method for producing a sintered ore in which an iron ore raw material, an auxiliary raw material, and a carbon material having a combustion initiation temperature of 550 DEG C or less are blended, said method comprising: the iron ore raw material containing 40-60 mass% of a high-crystal-water iron ore powder containing 4 mass% or more of crystal water; the high-crystal-water iron ore powder is a single variety having a particle size of 0.15 mm or less of 10 mass% or more, or a mixture of a plurality of varieties containing a variety having a particle size of 0.15 mm or less of 10 mass% or more in total relative to the high-crystal-water iron ore powder, wherein the content of the variety is 50 mass% or more in total relative to the high-crystal-water iron ore powder.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing sintered ore used in the iron and steel industry. Background Art

[0002] The iron ore sintering process is a process of sintering a material mixed with iron ore, a flux, and a carbon material as a solid fuel using the combustion heat of the carbon material in a sintering machine. Coke powder is usually used as the carbon material. As a dispersion of risks such as price fluctuations of raw coal and failures of coke manufacturing equipment, anthracite other than coke powder may sometimes be used.

[0003] On the other hand, in recent years, with the increasing awareness of environmental protection, for the purpose of reducing the environmental burden, which is different from the idea of risk dispersion, the diversification of carbon materials is being promoted.

[0004] For example, Patent Document 1 discloses a method including: when using high-crystalline water iron ore containing 4.0 mass% or more of crystalline water at 30% or more, containing 10 mass% or more of a solid fuel having a combustion start temperature lower than 450°C.

[0005] Patent Document 2 discloses a method including: mixing biomass with a limited amount of nitrogen and sulfur with iron ore and using a downward suction type sintering machine to manufacture sintered ore.

[0006] Patent Document 3 discloses a method including: combining a low-combustibility carbon material and a high-combustibility carbon material to manufacture sintered ore, and containing 2% or more of metallic iron or an iron-based raw material containing divalent iron ions in terms of inner count.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: International Publication No. 2010 / 106756

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2003-328044

[0011] Patent Document 3: Japanese Patent Application Laid-Open No. 2022-033594 Summary of the Invention

[0012] Problems to be Solved by the Invention

[0013] However, the following problems exist in the prior art.

[0014] In the technology disclosed in Patent Document 1, the particle size of pisolitic ore, which is a representative variety of high-crystalline water iron ore, is very coarse. Therefore, under the condition of only high-crystalline water iron ore, the air permeability becomes more than necessary. If a carbon material with a low combustion start temperature is used, there is a risk of reducing the yield.

[0015] In addition, in the technology disclosed in Patent Document 2, no research has been conducted on the variety, blending ratio, and properties of the ore, and the influence on the yield has not been considered.

[0016] In addition, in the technology disclosed in Patent Document 3, it only relates to using low-oxidation-degree ore as a heat source, and does not relate to the influence of particle size, etc. on the yield.

[0017] The present invention has been completed in view of the above circumstances, and its object is to provide a method for manufacturing sinter with high yield using high-crystalline water iron ore powder and a carbon material with a low combustion start temperature.

[0018] Means for Solving the Problem

[0019] The method for manufacturing sinter of the present invention that advantageously solves the above problems is a method for manufacturing sinter by blending an iron ore raw material, a subsidiary raw material, and a carbon material with a combustion start temperature of 550°C or lower. The method includes: the above iron ore raw material contains 40% by mass or more and 60% by mass or less of high-crystalline water iron ore powder, the high-crystalline water iron ore powder contains 4% by mass or more of crystal water, and the ratio of the high-crystalline water iron ore powder with a particle size of 0.15 mm or less is 10% by mass or more as a single variety, or a mixture of multiple varieties, and the mixture of multiple varieties contains 50% by mass or more of the high-crystalline water iron ore powder in total with a particle size of 0.15 mm or less and a ratio of 10% by mass or more of the variety.

[0020] It should be noted that for the method for manufacturing sinter of the present invention, the following methods can be more preferred solutions:

[0021] (a) The above iron ore raw material contains an iron ore raw material with a particle size of 0.15 mm or less in a proportion of 40% by mass or more and an Al2O3 component content of 1% by mass or less in a range of 20% by mass or less;

[0022] (b) The above carbon material contains a carbon material with a combustion start temperature of 550°C or lower in a proportion of 50% or less in terms of heat equivalent to coke;

[0023] (c) Among the above carbon materials, the carbon material with a combustion start temperature of 550°C or lower is any one or both of an organic resource other than fossil fuel and a carbon material manufactured using the above organic resource as a raw material.

[0024] Effect of the Invention

[0025] According to the method for manufacturing sintered ore of the present invention, a sintered ore is manufactured by mixing a high crystalline water iron ore having a specific particle size and a carbon material with a low combustion start temperature. Therefore, it is possible to manufacture an environmentally friendly sintered ore while maintaining the yield of the sintered ore. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a bar graph showing the influence of various mixing conditions in the examples on the yield of sintered ore. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, embodiments of the present invention will be specifically described. The following embodiments illustrate the compositions and methods for embodying the technical idea of the present invention, and the constitution is not limited to the following content. That is, various changes can be made to the technical idea of the present invention within the technical scope described in the claims.

[0028] When diversifying carbon materials used to reduce the environmental burden, organic resources other than fossil fuels and carbon materials manufactured using such organic resources (hereinafter referred to as biomass charcoal) have attracted attention. For biomass charcoal, carbon dioxide is absorbed during the growth of the plants that are its raw materials. Therefore, from the perspective of carbon neutrality, fuels using this biomass charcoal can be regarded as substances with no carbon dioxide emissions to the outside of the system. Thus, the use of biomass charcoal has also been studied in the iron ore sintering process where coke powder is usually used. As a characteristic of biomass charcoal, its combustion start temperature is lower than that of coke. The combustion start temperature of coke is in the range of 650 to 750 °C, whereas the combustion start temperature of biomass charcoal is approximately 550 °C or lower.

[0029] In the present embodiment, in the sintering process, a flux and a carbon material as auxiliary raw materials are added to iron ore, and continuously charged onto a sintering machine to form a sintering bed. After ignition at the upper end of the sintering bed, by sucking exhaust gas from the lower end, the combustion of the carbon material propagates from the upper end of the bed to the lower end, and the heat is used for the reaction between the iron ore and the flux and agglomeration. The exhaust gas suction from the lower end is performed using a blower. The sucked exhaust gas passes through a pipeline and is discharged from a chimney via a dust collector and a desulfurization / denitration device.

[0030] Biomass charcoal is characterized by its low combustion start temperature. This is because, compared with coke powder (derived from fossil fuels) usually used in the sintering process, biomass charcoal is porous and has a very large specific surface area. Therefore, a high combustion rate can be obtained even at a low temperature. Therefore, biomass charcoal shows a tendency not only to have a low combustion start temperature but also to have a high combustion rate after starting combustion.

[0031] Carbon materials with a high combustion rate increase the propagation speed of the flame in the sintering bed, thus increasing the FFS (flame front speed: the moving speed of the reaction zone downward). This indicates a shortening of the reaction time in the sintering bed. When the reaction time is shortened, the amount of molten liquid generated by the reaction of ore and flux decreases, or the flow distance of the generated molten liquid becomes shorter. Therefore, the molten liquid cannot fully function as a binder to bond the ores together, resulting in drawbacks such as a decrease in the yield rate.

[0032] On the other hand, iron ore contains crystal water components, which are contained in large amounts in goethite, etc. The crystal water in high crystal water iron ore is different from ordinary moisture in the sintering reaction and decomposes / volatilizes at 300 - 400 °C. It is known that the endotherm during decomposition / volatilization is close to the heat of vaporization of water. When sintering an iron ore raw material containing a large amount of high crystal water iron ore, it is necessary to additionally add a carbon material equivalent to the amount of heat corresponding to this endotherm. Therefore, an iron ore raw material containing a large amount of high crystal water iron ore is more susceptible to the properties of this carbon material. That is, when using biomass carbon under the condition of using high crystal water iron ore at a high ratio, the FFS becomes very high and the yield rate is likely to deteriorate. Generally, the air permeability of granulated iron ore can be evaluated by the ratio of the particle size below 0.15 mm contained in the ore. This is because fine powder below 0.15 mm is likely to become ungranulated powder or powder that peels off during drying in the layer after being charged into the sintering machine. Therefore, when using biomass carbon under the condition of using high crystal water iron ore, it is necessary to limit the particle size of the high crystal water iron ore in order to suppress the air permeability of the raw material and not make the FFS too high. To obtain this effect, the ratio of the particle size below 0.15 mm of the high crystal water iron ore is set to 10 mass% or more. On the other hand, in order to set the ratio of the particle size below 0.15 mm to more than 30 mass%, ore dressing and pulverization are required, and the cost will increase, so it is preferably set to 30 mass% or less.

[0033] In addition, compared with the case of only using biomass carbon, further effects can be expected when using a raw material with a large amount of fine powder. Generally, granulated products can be divided into: ore that becomes the core, and adhering powder attached to its surroundings. The above particle size range below 0.15 mm corresponds to the area of this adhering powder. It is reported that due to the fast combustion rate of biomass carbon, not only is the firing time shortened, but also incomplete combustion occurs due to the limited oxygen supply rate, resulting in a deterioration of the yield rate. Therefore, by using biomass carbon and a raw material with more than 0.15 mm, the probability of forming an internal filling type granulated particle in which biomass carbon exists inside the granulated particle and the adhering powder forms its surroundings increases. Thus, in order to burn the biomass carbon, it is necessary to make oxygen diffuse through the adhering powder layer to the surface of the biomass carbon, which can reduce the combustion rate of this biomass carbon. Thereby, incomplete combustion can be prevented and the heat input can be fully utilized.

[0034] According to the above content, the method for manufacturing sintered ore of the first embodiment is a method for manufacturing sintered ore in which an iron ore raw material, a subsidiary raw material, and a carbon material with a combustion start temperature of 550°C or lower are mixed. This method includes: the above iron ore raw material contains 40% by mass or more and 60% by mass or less of high-crystalline water iron ore powder, and this high-crystalline water iron ore powder contains 4% by mass or more of crystalline water. The proportion of the high-crystalline water iron ore powder with a particle size of 0.15 mm or less is 10% by mass or more for a single variety, or is a mixture of multiple varieties, and the mixture of these multiple varieties contains 50% by mass or more of the varieties with a particle size of 0.15 mm or less in the above high-crystalline water iron ore powder in total.

[0035] When the high-crystalline water iron ore powder in the iron ore raw material is less than 40% by mass, the impact on the yield of sintered ore is small. On the other hand, when the high-crystalline water iron ore powder in the iron ore raw material exceeds 60% by mass, coarse particles are generated during granulation, and there is a risk of disturbing the uniformity of gas flow in the packed bed during sintering. When the proportion of the variety with a particle size of 0.15 mm or less is less than 50% in the high-crystalline water iron ore powder, there is a risk of reducing the yield. The high-crystalline water iron ore powder can be a single variety or a mixture of multiple varieties within the allowable range of its conditions.

[0036] In addition, for high-crystalline water ore, from the aspect of the formation method of its ore deposit, it contains a large amount of gangue components. In particular, it is known that Al2O3 reduces the yield of sintering. In order to reduce this effect, it is preferable to mix ores with less Al2O3 and a large proportion of particles with a size of 0.15 mm or less. For example, as ores with a low proportion of Al2O3 and a large proportion of particles with a size of 0.15 mm or less, concentrates that have been treated by flotation, magnetic separation, etc., such as concentrate ores and pellet feed ores, can also be used. However, if such ores are mixed beyond the appropriate range, it will promote non-uniform sintering in the charging layer, and there is a risk of reducing the yield instead.

[0037] From the above viewpoints, the method for manufacturing sintered ore of the second embodiment further includes, in addition to the first embodiment: an iron ore raw material containing 40% by mass or more of particles with a size of 0.15 mm or less in a range of 20% by mass or less and having an Al2O3 component content of 1% by mass or less.

[0038] In the method for manufacturing sintered ore according to the third embodiment, as the carbon material, a carbon material having a combustion start temperature of 550°C or lower is included in a proportion of 50% or less in terms of heat equivalent to coke. Thereby, the yield of the sintered ore is improved, which is therefore preferable. From the viewpoint of environmental friendliness, the lower limit does not include 0. More preferably, the carbon material having a combustion start temperature of 550°C or lower is in the range of 30% or more and 40% or less in terms of heat equivalent to coke.

[0039] Examples

[0040] As the iron ore raw material to be blended, iron ores having the particle sizes and compositions shown in Table 1 were used, that is, ores A to C and concentrate D were used, and the above-mentioned concentrate D was increased in fines and reduced in Al2O3 by beneficiation treatment. Based on the blending ratio of the iron ore raw materials, considering the difference in the content of crystal water, the coke equivalent heat of the carbon material to be blended was adjusted so that the heat other than its decomposition heat was constant. As the auxiliary raw material, limestone was used, and the blending amount was determined so that the mass ratio of CaO to SiO2 in the total of all raw materials was 2.0. After blending the iron ore raw material, the auxiliary raw material, and the carbon material and conducting a batch-type sintering test, the yield thereof was measured.

[0041]

[0042] Table 2 shows the blending ratios of the respective iron ore raw materials and the blending ratio of the biomass charcoal in the carbon material. The blending ratio of the biomass charcoal is expressed as a percentage in terms of heat equivalent to coke. In Figure 1The sintered product yields under various conditions are shown in the form of a chart. The product yields of the inventive examples are all 70% by mass or more. Among T1 to T9, biomass charcoal is used in half of the carbon materials in the mixture, and the remaining part is coke. In addition, for other levels of biomass mixing ratios, they are mixed in such a way that T10 is 40%, and T11 and 12 are 60%. T6 is a reference example. Under the condition of mixing 70% by mass of ore C, the remaining part is coarse ore B. T6 shows a product yield exceeding 75% under the condition of containing 50% biomass. It is considered that this is because ore C contains a large amount of fine powder and the FFS does not become too high. In contrast, in T4 and T5, concentrate D is not added, ore C is reduced to 50 - 60% by mass, and the remaining part is ore A and ore B. T4 and T5 contain 30 - 40% by mass of coarse ore B, and the FFS becomes high, so the product yield drops below 70% by mass. On the other hand, for T1 to T3 containing 20% by mass or more of fine - grained ore A in the ore, although the product yield is slightly lower than that of T6 in the reference example, it can still be maintained at 70% by mass or more. T7 to T9 are conditions where 20% by mass of ore A and 20% by mass of ore B are each mixed, and concentrate D is varied in the range of 10 - 30% by mass, and the remaining part is ore C. Compared with T3 without concentrate D, the product yields of T7 and T8 are significantly increased. On the other hand, in T9 containing 30% of concentrate D, the product yield is reduced compared with T7 and T8. It is considered that this is because a large amount of concentrate D is mixed, so segregation occurs during granulation, and uneven strength is generated in the sinter cake. T10 and T11 change the biomass ratio. T3 and T10 are levels where the iron ore raw materials have the same mixture and the biomass charcoal is 50% or less. Their product yields are higher than that of T11 with 60% of biomass charcoal. T12 is obtained by replacing a part of ore C in T11 with concentrate D, and its product yield is lower than that of T8 with the same mixture and 50% biomass.

[0043]

Claims

1. A method for manufacturing sintered ore, which is a method for manufacturing sintered ore by mixing an iron ore raw material, a subsidiary raw material, and a carbon material with a combustion start temperature of 550°C or lower, the method comprising: The iron ore raw material contains 40% by mass or more and 60% by mass or less of high crystal water iron ore powder, and the high crystal water iron ore powder contains 4% by mass or more of crystal water. The high crystal water iron ore powder is a single variety with a particle size of 0.15 mm or less at a ratio of 10% by mass or more, or a mixture of multiple varieties, and the mixture of multiple varieties contains 50% by mass or more of the high crystal water iron ore powder in total, and the proportion of the variety with a particle size of 0.15 mm or less is 10% by mass or more.

2. The method for manufacturing sintered ore according to claim 1, wherein The iron ore raw material contains, in a range of 20% by mass or less, an iron ore raw material with a particle size of 0.15 mm or less at a ratio of 40% by mass or more and an Al2O3 component content of 1% by mass or less.

3. The method for manufacturing sintered ore according to claim 1, wherein The carbon material contains, in a proportion of 50% or less in terms of heat equivalent conversion with coke, a carbon material with a combustion start temperature of 550°C or lower.

4. The method for manufacturing sintered ore according to claim 1, wherein Among the carbon materials, the carbon material with a combustion start temperature of 550°C or lower is any one or both of an organic resource other than fossil fuel and a carbon material manufactured using the organic resource as a raw material.

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